The present invention relates to computer animation. More specifically, the present invention relates to object manipulation, and in particular object squash and stretch methods and apparatus when bending objects.
Throughout the years, movie makers have often tried to tell stories involving make-believe creatures, far away places, and fantastic things. To do so, they have often relied on animation techniques to bring the make-believe to “life.” Two of the major paths in animation have traditionally included, drawing-based animation techniques and physical animation techniques.
Drawing-based animation techniques were refined in the twentieth century, by movie makers such as Walt Disney and used in movies such as “Snow White and the Seven Dwarfs” (1937) and “Fantasia” (1940). This animation technique typically required artists to hand-draw (or paint) animated images onto a transparent media or cels. After painting, each cel would then be captured or recorded onto film as one or more frames in a movie.
Physical-based animation techniques typically required the construction of miniature sets, props, and characters. The filmmakers would construct the sets, add props, and position the miniature characters in a pose. After the animator was happy with how everything was arranged, one or more frames of film would be taken of that specific arrangement. Physical animation techniques were developed by movie makers such as Willis O'Brien for movies such as “King Kong” (1933). Subsequently, these techniques were refined by animators such as Ray Harryhausen for movies including “Mighty Joe Young” (1948) and Clash Of The Titans (1981).
With the wide-spread availability of computers in the later part of the twentieth century, animators began to rely upon computers to assist in the animation process. This included using computers to facilitate drawing-based animation, for example, by painting images, by generating in-between images (“tweening”), and the like. This also included using computers to augment physical animation techniques. For example, physical models could be represented by virtual models in computer memory, and manipulated.
One of the pioneering companies in the computer aided animation (CAA) industry was Pixar. Pixar developed both computing platforms specially designed for CAA, animation software, and rendering software now known as RenderMan®. RenderMan® was particularly well received in the animation industry and recognized with two Academy Awards®. While RenderMan® was focused upon rendering, the creation of images from geometric models, the animation software developed for in-house use focused upon allowing animators to specify (“animate”) the geometric models. The geometric models typically represent objects in a scene, characters in a scene, positions of objects and characters, manipulation of objects and characters, lighting, textures, and the like.
Techniques for object manipulation known in the industry as “squash and stretch,” was first described by Walt Disney animators in the 1930s. These techniques were attempts to allow animators to deform an object in motion to attempt to mimic “natural” changes of an object as it progressed “through an action.” Attempting to maintain the volume of an object while in motion enables animators to convey the pliable nature of the object.
In the field of 3D animation, presently available animation tools have been better suited to working with solid objects like cars and teapots as they produces rigid looking volumes in motion. Typically, squash and stretch techniques were not needed for solid or rigid objects.
Prior to the present invention animators would have access to separate and very specific controls that could be individually operated on to deform an object. For example, animating an arm, in the forearm you would have three separate “scale” controls to change the shape: length, width and thickness. The animators would also have the same controls in the forearm. The animator would then have to control the relationships between those six controls to try and achieve the function of the squashing and stretching. For example, to stretch the arm, some of the controls would be set in the positive direction, some of the controls would be set in the negative direction and the animator would be responsible for sorting out which direction each control should be set. Unfortunately, the six controls treat the arm as two separate pieces and the resulting shape is highly undesirable.
FIGS. 1A–C illustrate inferior results of manual prior art techniques. More specifically, FIG. 1A illustrates an example of an arm having an upper portion, and a lower portion in a rest position. FIG. 1B illustrates the arm that has been squashed using non-integrated object squash and stretch operations, such as scale. As can be seen in FIG. 1B, one problem with traditional techniques is that the elbow volume is not properly maintained. FIG. 1C illustrates the arm that has been stretched using non-integrated object squash and stretch operations, such as scale. As can be seen in FIG. 1C, one problem with traditional techniques is that the elbow volume is improperly maintained.
Recently third party 3D animation packages like Alias/Wavefront's Maya have begun to support a customization of their controls that allows animators to write custom command code to “blend shapes.” The inventors have considered that in light of the present disclosure, theoretically, using commercially available packages, they might be able to take an object and compensate for squash and stretch, however not without a lot of labor for preparing an object model, and writing custom code.
The inventors of the present invention have determined that methods for automated and integrated squashing and stretching of objects is needed in the context of 3D animation, without the drawbacks illustrated above.